During build, how to create a directory for a file which is generated by some COMMAND? - cmake

Question

I'm writing a custom command in CMake to convert a file to binary format at build time. However, the tool I'm using requires directory for a file to be pre-existed; it doesn't create a directory automatically.
Currently my CMake macro looks like this:
MACRO(ConvertToBinary _name)
ADD_CUSTOM_COMMAND(
OUTPUT ${CMAKE_BINARY_DIR}/${_name}.bin
COMMAND ${EXE_DIR}/toBinary -i ${CMAKE_CURRENT_SOURCE_DIR}/${_name} -o ${CMAKE_BINARY_DIR}/${_name}.bin
DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${_name}
)
ENDMACRO(ConvertToBinary)
This macro doesn't work for _name parameter equal, e.g., to "test/sample.txt", because the tool is run with test/ folder under ${CMAKE_BINARY_DIR} being not existed.
How to create the directory before the tool, generating the file, is run?
I have tried to overcome the problem by pre-creating the file (and directory) with the help of CMake. So the tool will be run with the directory created, and can override the output file. I have tried the following:
MACRO(ConvertToBinary _name)
ADD_CUSTOM_COMMAND(
OUTPUT ${CMAKE_BINARY_DIR}/${_name}.bin
FILE(WRITE ${CMAKE_BINARY_DIR}/${_name}.bin "Dummy")
COMMAND ${EXE_DIR}/toBinary -i ${CMAKE_CURRENT_SOURCE_DIR}/${_name} -o ${CMAKE_BINARY_DIR}/${_name}.bin
DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${_name}
)
ENDMACRO(ConvertToBinary)
But it did not work. I can't find information on how to create file at build time with CMake, so any help is appreciated.

Answer 1

In CMake you may extract directory component of the file and create this directory.
Below code can be used for a tool, which generates a file but doesn't create directory for it.
# Assume some tool generates file '${file}', but don't create directory for it.
#
# Extract directory component for a file
get_filename_component(_dir ${file} DIRECTORY)
add_custom_command(OUTPUT ${file}
COMMAND ${CMAKE_COMMAND} -E make_directory ${_dir} # Create output directory
COMMAND <tool-which-generates-file> ... ${file}
)
See also that question about ways for create a directory in CMake.